Bulk Bash DNS checker

dns_check.sh

#!/bin/bash
domain_list='shortlist.txt'

declare -a resol
resol=('8.8.8.8' '8.8.4.4' '1.1.1.1' '1.0.0.1' '9.9.9.9' '149.112.112.112') #multiple resolvers

for domain in `cat $domain_list`
do
        ns_ip=${resol[`shuf -i0-5 -n1`]} #select resolver
        registrar_detail=`whois $domain | grep -i "registrar:" | tail -n1 | awk  '{print $2 $3}' | tr , " "` #fetch registrar. improvement needed 
        ip=`dig @$ns_ip +short $domain | tail -n1`; #get IP
        if [ ! -n "$ip" ]
        then
                echo "$domain,$registrar_detail,No DNS,,"; #if no IP, no DNS 
        else
                #assembling all data and also adding NETNAME and NameServers to it
                echo "$domain,$registrar_detail,$ip,"`whois $ip | grep -i netname | awk '{print $2}'`","`dig @$ns_ip +short ns $domain`;
        fi
done   

Running it as "sh dns_check.sh" may not work due to array usage. use ./dns_check.sh instead if not working.